Process for making white clouded



Patented Dec. '15, 1942 UNITED STAT PROCESS FOR MAKINGWHITE CLOUDEDENAMEL Ignaz Kreidl, Cleveland, Ohio; vested in the Alien PropertyCustodian No Drawing. Application August 21, 1936, Serial No. 97,286.In.

' Claims.

This invention relates to a process for makin white clouded enamel, moreparticularly iron enamel; by gas clouding, the white clouding beingbrought about, by development of small gas bubbles from substances whichdecompose at the burning-in temperature, which substances are added tothe enamel composition on the mill instead of the usual solid whiteclouding agents.

The present invention depends upon the discovery that by means ofcertain metal oxides or compounds thereof, such as more particularlyoxides of iron, antimony, cerium, uranium,

Austria September 25, 1935 arsenic or mixtures containing these oxides,the

whiteness value of the gas clouding can be very considerably enhanced,whence a decolourising efiect may be allied to gas clouding means which.have' a colouring effect (for example may give rise to the formation ofsubstances having a colouring action such as carbon compounds having acolouring effect), obviously in consequence of the better burningbrought about by their oxidising effect at the burning-in temperature.

The process according to the invention consists in this that metaloxides, such as antimony I oxide, uranium oxide, cerium oxide, ironoxide,

arsenic oxide, or compounds of these oxides with other metal oxides, areintroduced into the enamel independently of the fact whether thecompound added as gas clouding agent contains one of these oxides ornot, the introduction of these oxides into the enamel however being madein such small quantities that in the enamel the oxide is contained onlyin a quantity such that any clouding that may be attributable to theoxide itself is without influence, but nevertheless in a quantitysuflicient for the oxide to enhance the whiteness value.

Processes for making white clouded enamel are already known in which theclouding action of .the solid substances usual as clouding agents forenamel, such as for example the oxides of tin,

. zirconium, antimony or the like, is strengthened by addition in themill of substances which produce their eiiect by gas clouding. Processesare also known in which compounds or complexes of the metals of thewhite'clouding agents group, which split of! gases even in the slip atthe buming-in temperature. are added to the enamel on the mill inquantities which are so small that the solid residue can bring about noclouding effects, whilst on the other hand the volatile porgas cloudingagent introduced with the oxide, as a result of which a correctadjustment to the whiteness value of the enamel, at which the presentinvention aims, is not possible. In these known processes the eflect mayarise that either too little metal oxide is introduced into the enamelwith correct. addition of clouding agent, or too much clouding agentmust be added with the correct addition-of metal oxide.

In the process according to the present invention the action of theseoxides and compounds is an action which is quite different-in naturefrom that of a clouding action. The action of these oxides appearsirrespective of whether these oxides or compounds are added to theenamel on the mill or are fused with the raw substances forming theenamel. The action also already appears with such small quantities thatany clouding efiect attributable to these oxides themselves can beignored. How different this action is from a clouding action is apparentfrom ing to far below 1%, an increase of this content above 1% bringingwith it no further advantages as regards the action at which theinvention aims. Preferably an addition is made in such a small quantitythat, independently of the fact whether, the compounds added as gasclouding agent contain one of these oxides. or not, the total quantityof these oxides does not exceed 1%, and

advantageously lies below 1%. v

The action of these substances is obviouslyto be attributed to this thatin the quantities in which they exert their. efiect in the processaccording to the invention they are without injurious auxiliary efiecton the slop or a constituent of the slop.

Not only however are the oxides of antimony, uranium, iron, cerium andarsenic, all of which are capable of forming several oxidation stages,

- suitable for carrying out the process according tion suiiices owing tothe development of small!v gas bubbles to impart a white clouding as aresult of these bubbles.

In these known processes the quantity of metal oxide for examplestands'in a definite ratio to the quantity of gas clouding agent or ofthe decomposable portion which is active as gas clouding agent and'thequantity to be added as clouding agent depends on the quantity oi the tothe invention, that is to say for introduction into the enamel, but alsomixtures containing such oxides and also compounds of these oxides maybe.used, more particularly their compounds with other oxides, e. g.antimoniates or the like.

The process according to the invention is particularly suitable; forthose methods of making white clouded enamel in which gas cloudingagents are used in conjunction with enamel frits, which in the sloppossess larger colloidal portions than normal enamel fri-ts. For examplethe colloidal properties or the colloidal portions mately fluorine witha proportion between 4 alkali and boric acid'ofdta parts alkali to onepart boric acid. By raising the fluorine content to approximately doublethe amount, that is to say to about 12% fluorine for example, frits in acolloid-dike state with a normal ratio of alkali to boric acid may beobtained, the fluorine how'- ever preferably being introduced in theform of alkali fluosilicate, such as for example sodium iluosilicate.

Examples Grams (1) Enamel mass 1,000 Water 500 Benzidine 0.25 Uraniumoxide 4 Clay 100 are ground up on the mill and thereupon applied in theusual manner and burnt in.

Grams (2) Enamel mass 1,000 Water 500 Methylene blue 0.25 Antimony oxide(or sodium antimoniate) 5 Clay 100 are ground up on the mill andthereupon applied in the usual manner andburnt in.

In these examples a frit particularly suitable for gas cloudings, and infact a fluorine-rich frit of highly colloidal properties was used asenamel frit, in which the fluorine content originates frflm alkalifluorides or alkali silicoiluoi'ides. However, the invention of courseis not limited to such frits.

The additions forming the subject of the invention may be added to theenamel frit or to the enamel slip not only on the mill but also.

already previously to a constituent of the enamel slip, or may also befused together with the raw substances forming the enamel.

What I claim is:

1. In a method 0! producing a gas clouded vitreous enamel, the step ofincorporating in the enamel batch an organic gas clouding agent and acompound containing antimony and ongen in an amount less than 1% of theenamel to remove discoloration caused by the residue resulting from Vthe decomposition of said gas clouding agent.

2. In a process of producing a gas clouded vitreous enamel from a slipincluding an organic gas clouding agent and a frit, in which the frit isproduced by melting together a mixture of ma- Grams (3) Enamel mass1,000

Water 500 o Naphthol 0.25 Iron oxide 3 Clay 7 100 are ground up on themill and thereupon applied are ground up on the mill and thereuponapplied in the usual manner and burnt in.

- Grams (5) Enamel mass 1,000

1 Water 500 Methylene blue 0.25 Cerium fluoride 5 Clay 100 are ground upon the mill and thereupon applied in the usual manner and burnt in.

terials, the step of adding to the frit materials before melting acompound containing antimony and oxygen in an amount less than 1% of theenamel to remove discoloration caused by the residue resulting from thedecomposition of said gas clouding agent.

3. In a method of producing a gas clouded vitreous enamel, the step ofadding to the enamel slip an organic gas clouding agent and a compound,containing antimony and oxygen in an amount less than 1% of the enamelto remove discoloration caused by the residue resulting from thedecomposition of said gas clouding agent. 4. An enamel slip for thepreparation of gas clouded vitreous enamels, said slip containing anorganic-gas clouding agent being capable of forming a discoloringresidue on firing the enamel and a compound containing antimony andoxygen in a quantity less than 1% of the enamelto remove discolorationcaused by said residue on firing the enamel.

5. In a. process of preparing' clouded enamels normally affected by adiscoloration resulting from the decomposition of organic compounds inthe enamel, said process comprising the melting of the raw batch atelevated temperatures, introducing into the enamel mass an opaciflerfree from antimony, and firing the enamel mass, whereby anon-homogeneous diouded enamel is obtained: the new step of adding tosaid enamel mass intermediary the first and second heating an agentcapable of preventing said discoloration by reacting with said organiccompounds, said agent comprising an oxide of antimony in an amount ofless than 1% by weight of said enamel mass.

IGNAZ KREIDL.

